The saints in heaven aren’t dead, they are eternally alive in God. And yes they can pray for us, just as any saint on earth can pray for us.
The only persons alive in heaven from earth are:
Translated Alive without seeing Death:
Enoch (OT) - Gen. 5:24; Heb. 11:5 KJB
Elijah (OT) - 2 Kin. 2:1-12 KJB
Resurrected (made alive from death), and taken back to heaven:
Moses (OT) - Num. 20:8-12, 27:13, 31:2; Deu. 4:21-22, 31:2,14,16, 32:51-52, 34:1-8; 1 Sam. 2:6; Jhn. 11:25-26; Mat. 17:1-12; Mar. 9:1-13; Luk. 9:27-36; Rom. 5:14; 2 Pet. 1:16; Jud. 1:9 KJB
Jesus (NT) - Eternal Heavenly Trio (JEHOVAH Elohiym) Col. 2:12; 1 Pet. 1:21; 1 Cor. 6:14; Act. 2:24, 3:15, 13:33; Heb. 13:20; (The Father) Act. 4:10; Eph. 1:20; Rom. 6:4; Gal. 1:1; 1 Thes. 1:10; (The Son) Jhn. 2:19, 10:18; (The Holy Ghost) Rom. 8:11; 1 Pet. 3:18; See also: Mat. 28:1-20; Mar. 16:1-20; Luk. 24:1-53; Jhn. 20:1-31; 1 Cor. 15:20,23 KJB
Firstfruits (NT) - Mat. 27:50-53, 28:1-4; Isa. 26:19; (for Jesus, see also Psa. 40:6; Heb. 10:5; Gal. 4:4); Psa. 68:8,17-21 (vs 21., see Gen. 3:15); compare Psa. 68:18 to Eph. 4:8-10; & Lev. 23:9-14; 15-22 (Firstfruits) to 1 Cor. 15:21-23. See also Psa. 24:1-10 (Victory Train into New Jerusalem), with Psa. 98:1-3; Col. 2:15. See also Acts 1.
There are no others. All else are deceased and await their resurrection, like as King David:
Act 2:29 Men and brethren, let me freely speak unto you of
the patriarch David, that
he is both
dead and
buried, and
his sepulchre is with us unto this day.
Act 2:34 For
David is not ascended into the heavens: but he saith himself, The LORD said unto my Lord, Sit thou on my right hand,
Act_13:36 For
David, after he had served his own generation by the will of God,
fell on sleep, and
was laid unto his fathers, and
saw corruption:
Act 2:42 And
they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers.
Jesus said so:
Joh 5:28 Marvel not at this: for the hour is coming, in the which
all that are in the graves shall hear his voice,
Joh 5:29 And
shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation.
Job by the Holy Ghost said so:
Job_20:11
His bones are full of the sin of his youth, which shall
lie down with him in the dust.
Job 17:13 If I wait,
the grave is mine house: I have made
my bed in the darkness.
Job 14:5 Seeing his days are determined, the number of his months are with thee, thou hast appointed his bounds that he cannot pass;
Job 14:6 Turn from him, that
he may rest, till he shall accomplish, as an hireling, his day.
Job 14:7 For there is hope of a tree, if it be cut down, that it will sprout again, and that the tender branch thereof will not cease.
Job 14:8 Though the root thereof wax old
in the earth, and the stock thereof die
in the ground;
Job 14:9 Yet through the scent of water it will bud, and bring forth boughs like a plant.
Job 14:10 But
man dieth, and
wasteth away: yea,
man giveth up the ghost, and where is he?
Job 14:11 As the waters fail from the sea, and the flood decayeth and drieth up:
Job 14:12 So
man lieth down, and
riseth not:
till the heavens be no more,
they shall not awake, nor be raised out of their sleep.
Job 14:13 O that thou wouldest
hide me in the grave, that thou wouldest
keep me secret,
until thy wrath be past, that thou wouldest appoint me a set time, and remember me!
Job 14:14
If a man die, shall he live again? all the days of my appointed time will I wait,
till my change come.
Job 14:15 Thou shalt call, and I will answer thee: thou wilt have a desire to the work of thine hands.
Paul quotes Job:
1Co 15:51 Behold, I shew you a mystery; We shall not all
sleep, but
we shall all be changed,
1Co 15:52 In a moment, in the twinkling of an eye,
at the last trump: for the trumpet shall sound, and
the dead shall be raised incorruptible, and we shall be changed.
The Wrath of God is the 7 Last Plagues; Rev. 15-16.
The Heaven of this earth does not pass away until Jesus returns in power:
2Pe_3:10 But
the day of the Lord will come as a thief in the night;
in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
2Pe_3:12 Looking for and hasting unto the coming of the day of God,
wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat?
Rev_6:14 And
the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places.
Paul said:
Col 3:3 For ye are dead, and your life is hid with Christ in God.
Col 3:4
When Christ, who is our life,
shall appear, then shall ye also appear with him in glory.
Heb 11:39 And these all, having obtained a good report through faith,
received not the promise:
Heb 11:40 God having provided some better thing for us,
that they without us should not be made perfect.
1Th 4:13 But I would not have you to be ignorant, brethren, concerning
them which are asleep, that ye sorrow not, even as others which have no hope.
1Th 4:14 For if we believe that Jesus died and rose again, even so
them also which sleep in Jesus will God bring with him.
(ie back to heaven when He returns for them)
1Th 4:15 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent
them which are asleep.
1Th 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and
the dead in Christ shall rise first:
1Th 4:17
Then we which are alive and remain shall
be caught up together with them in the clouds, to meet the Lord in the air: and
so shall we ever be with the Lord.
The Bible is clear. Whomever you think you are praying to (including Mary, also dead), or asking to pray for you, are dead. They cannot hear you (Ecc. 9:5-6,10; Psa. 146:4; &c.)
Job_14:21 His sons come to honour, and he knoweth it not; and they are brought low, but he perceiveth it not of them.