Not at the same level. Ublock can remove way more granular spam and ads than pihole, which is limited at DNS requests. I use both... Running Firefox of course.
de v3 versions, obviously. Mozilla has no intentions of implementing it, and if chrome kills v2, it's not impossible that mozilla can hit them with an anti trust case and win, considering this is arguably what that would be.
But it will probably start to break on individual shitty websites over time, as per usual unfortunately.
To an extent. But it wouldn't surprise me at all if sometime in the near future they force the use their own DNS servers within their browser instead of respecting your network configuration.
The best solution to circumventing Chrome's bad behavior is to not use it.