Will this improve my home Wi-Fi speed?

No. It extends your home Wi-Fi coverage, not speed. Your connection may even be slightly slower than your main network, but it’s still very usable for browsing, streaming, and basic work.

Also: Slow Wi-Fi? I found 10 proven ways to fix your internet this weekend (most are free)

Can any Android phone do this?

Most modern Android phones support Wi-Fi hotspot features.

Will this drain my Android phone’s battery?

Yes, quickly. Keep the phone plugged in if you plan to use it as a permanent Wi-Fi extender.

Should I just buy an extender?

If you already have an old phone and just need basic coverage in one problem area, no. If you need reliable, high-speed performance across your home, a dedicated Wi-Fi extender or mesh system is better.