Need help for advanced understanding of french defence

Right now I play the Qb6 advanced, Bd6 Ne2 exchanged and blackburne rubinstein.

I think my knowledge of french defence is pretty limited so I want to understand it more.

1) What to play against the classical variations instead of blackburne? dxe4 Nf6 gxf6? Closed  variations with are Nf6? Winawer? Open tarrash? Or do I stay with the blackburne for now?

2) How to face the main line advanced? Is the cxd4 Ne7 Nf5 ok here or do I have to learn c4 lines?

3) I need ideas in the advanced french. Right now I'm just spamming Nc6 Qb6 cxd4 Ne7 Nf5. I almost NEVER used Nh5 cuz I don't understand it. Can anyone explain it's advantages over Ne7?I almost never use the french bishop, countering pins with Qb6 and double cxd4 spam. The bishop is used only if my opponent opens the a6 square for him or in the milner-barry gambit. When do I check with the DSB instead of playing Be7?

4) If in the exchange Bd6 Ne2 which setup is better? Queenside castle or Bf5 Bxd3? Where is the best square for LSB? f5 or g4?

5) What to do against Qe2 and KIA? I never faced them yet but I want to have prep ahead

What the bleep is the Blackburne? The fact that you mentioned the Rubinstein tells me you are confusing names (or else it's another of Chess.com's incorrect namings, just like how there is no Sicilian "French" variation).

It's either the Rubinstein (3...dxe4 4.Nxe4 Nd7) or the Fort Knox (3...dxe4 4.Nxe4 Bd7 intending 5...Bc6)

As far as the advanced - you cannot pre-meditate all those moves. It depends on White.

After 1.e4 e6 2.d4 d5 3.e5 c5 4.c3, there are a number of things to keep in mind:

1) If you intend to play the ...Qb6 line, play 4...Qb6 instead of 4...Nc6 and 5...Qb6. If you intend to play the ...Bd7 line, then it doesn't matter. By playing 4...Qb6 5.Nf3 Nc6, you avoid the sideline 4...Nc6 5.Be3 Qb6 6.Qd2. By moving the Queen first, you avoid 5.Be3 because the b2-pawn hangs and this is NOT a case of the pawn being poisoned. So play 4...Qb6 first and 5...Nc6 after that. You also will need a line against 4.Nf3. Typical is 4...cxd4 5.Bd3 Nc6 with Qb6 and Bc5, etc.

2) After 1.e4 e6 2.d4 d5 3.e5 c5 4.c3 Qb6 5.Nf3 Nc6, it all depends on White's 6th move:

A) After 6.Be2, then 6...cxd4 7.cxd4 Nge7 (the old 7...Nh6 is now best answered by 8.Bxh6!!) and now best for White is 8.Na3 Nf5 9.Nc2 as he has no time for 8.O-O? Nf5 and White is losing material

B) After 6.Bd3, you can decline the gambit with 6...Nh6 or you can accept with 6...cxd4, against which you have 7.O-O or 7.cxd4 Bd7 8.O-O Nxd4 and now 9.Nxd4 Qxd4 or 9.Nbd2 Nc6!

C) After 6.a3, the old 6...Nh6 is now under a cloud. Black needs to take the 6...c4 approach.

So again, to answer your question about ...c4 vs ...Ng8-e7-f5, the answer is, IT DEPENDS ON WHAT WHITE DOES!

There is no opening where you can follow a cookie cutter approach or a "script". Chess doesn't work that way!