AE86 4age engine not starts crank ok backfires to air intake

[Ryo]

Hello,
I decided to help my friend with his kouki AE86 with 4age the car was sitting for 3-4 years without movement. After discovering the fuel pump is dead and was replaced the engine finally started. First days have been okay with engine running good but after that issues appeared that it got harder to start. What i noticed most that when i started it it was going on 3 cylinders after a while running it catched on all four making some weird noise. Now the engine wont start at all and recently i see when i got the hose of air intake down that it fires to air intake. Another thing i noticed that spark plugs are full of fuel and when i checked engine oil level i smell not burned fuel in it. Another discovery i made i see oil comming from the middle of the distributor cap rotor. Spark was always okay on all 4 cylinders.

What was done so far:
- replaced fuel pump
- replaced engine oil and filter
- replaced all spark plugs
- replaced sparkplug wires
- replaced distributor cap and the thing in the middle (don't know the word in english for it right now)

i have read some things in 4age manual but was hoping someone can point me more to what issue or issues i am looking for.

My guess is timing belt slipped some teeth - timing off, distributor full of oil because of leakage. Can't explain the weird sound after running on 3 cylinders after the 4th catches. The smell of fuel in oil (damaged piston rings?)

I know the engine was rebuilded before the long stay and was running great.

Any help is greatly appreciated. Thank you.