Which firestick to buy ?

depends on your tv resolution. if it doesn't support 4k buy an fhd firestick

guys are you aware of any fire sticks or similar devices that allow me to install pikash0w or similar apps  for viewing on tv
I have a vu tv with google os and it is painfully slow 

Go for 4K fire tv stick for future proofing if not much price difference.

I bought 3rd gen for Rs.1500 last year, and 4k Max for Rs.3000.

4k Max is slightly faster and future proof if you want to watch in 4K 

however storage space is limited to 8GB which restricts how many apps you can install and this is exactly same as base version.

However with both devices, the alexa button stopped responding after 11 months of usage. The quality has degraded a lot compared to early firestick versions..

none

Firestick 4K (Max variant if you have a good branded TV(