- Did he paint the wall before his friend came?
- Did he paint the wall before his friend come?
- Had he painted the wall before his friend came?
- Had he painted the wall before his friend come?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
For all "standard" varieties of English, only before he came is valid. But you will sometimes hear come in similar "Past Tense" contexts in the UK...
1: We were in the pub last night when this guy come over and picked a fight with us
It's worth noting that although the first highlighted verb there looks like an "Unmarked Infinitive" (the non-inflected "base" form, but without the "infinitive marker" to), it's probably better analysed as just a different pronunciation of Past Tense came. I say that because you'll also sometimes hear the true "Present Tense used as Past" version used consistently...
2: ...when this guy comes over and picks a fight with us <==Ungrammatical, but not uncommon
...but I doubt I've ever heard the permutation comes + picked. And although both the above sound perfectly "natural" to me (albeit quite obviously "ungrammatical"), I can't say the same for #1 with other verbs. For example, I'm sure I've never heard either of...
3: * ...when this guy walk over and picked a fight with us <==VERY non-idiomatic!
4: * ...when this guy walks over and picked a fight with us <==VERY non-idiomatic!
Note that #1 and #2 above are primarily associated with uneducated speakers (or [semi-]facetious imitation thereof) - it's not particularly associated with any specific regional dialects.
TL;DR: The only "grammatically correct" version is...
5: We were in the pub last night when this guy came over and picked a fight with us
But "uneducated" native speakers often use Present as Past. And with certain specific verbs (come / came, run / ran), some people just enunciate the Present tense version even when they're using the explicit Past form with other verbs
About part number one of your question:
I've just searched for sentences like these in literature and found no one with "come" but with "came" found some examples:
"Did you see them off, before you came away?"
"Did you know Occula before you came to Bekla?"
‘Did you ever get to Gori before the Russians came?’ he asked Davit, in Georgian.
About second part of your question:
Had Georgiana warned him before he came up?
Had I found out before I had come to know the boy, I am unsure how I would have reacted.”
So as I can see by examples from literature you need to use version with "came" in this situation or use "had come" like last example.