Yes.
Spike and Apple Bloom do not go on a date in any episode. However, the is undoubtedly fanfiction on the subject, which can probably be found on the fimfiction website.
The very first episode "Friendship Is Magic- Part 1", all of the Mane Six are introduced and it is revealed that Spike is attracted to Rarity.
It is 'Solid Serenade'
It's an episode called Seeing Red, episode 19 of season 6.
Episode 17 of season 5, "Forever."
Probably not. MLP is one of those shows where you don't have to see the previous episode to understand what's going on. So if they start dating, they can't date for multiple episodes unless it is a 2-part show. For example, let's say they start dating in episode 11, somebody may not have seen episode 11, but they decide to watch episode 12. If they are still dating in episode 12, the person who missed episode 11 has no clue why Rarity and Spike are now "in a relationship". Also, they refer to Spike multiple times as a "baby dragon". The Hub cannot have a teenage pony date a baby dragon. That is totally inappropriate and does not belong in a kids' show.
Spike Lee
They have sex for the first time together in the episode Smashed.
Season 2, episode 3.
Angel (Angelus) sired (turned into a vampire) Drusilla who in turn sired Spike (William). Spike traveled with Drusilla, Angel, and Darla around the 1880's. So essentially Angel has always been aware that Spike was a vampire.
"Dead Things" is the 13th episode of season 6 of the television series Buffy the Vampire Slayer.
Yes, he does in Season 5 does Buffy know?