No.
The description above is making a situation appear to exist that actually doesn't.
Try this:
The party (A1,B1,C1,D1) are now all back in time ten days. As they now exist at the same time as their original selves (who have not yet experienced the events above), I will be rename them to...
Wait.
Did the two PCs that didn't go through the portal change the events the original party went through? If so, you have a time paradox on your hands (to be resolved in whatever fashion makes the most sense). If not, then the people who were sent back in time ten days wouldn't be able to meet...
No.
1. Conditions (whether beneficial or harmful) aren't a thing a creature loses (or counts as not having) because of what another creature has.
2. Unseen Attackers and Targets doesn't apply here because mechanically, the second benefit of the invisible condition doesn't care if you are...
The rules don't cover this interaction, so it's ultimately your decision what happens.
That being said, creature reverts to its normal form in the closest space/square that can accommodate said form is the ruling I go with.
While I wouldn't have a problem with any class using those stats, the stats to me seem to suggest a melee ranger first and foremost, then any of the martial or heavy armor clerics, then fighter.
Counterspell and Dispel Magic are means to interrupt magic that only people able to cast magic (or have the appropriate magic item(s)) can do.
The poster (and thread) is referring to bringing back a way to interrupt magic which once existed in the game (but currently doesn't) that anyone can...
Carrying Capacity mattering for grapple movement means that mechanically, a roc possibly cannot pick up a elephant and definitely cannot pick up a whale, which goes against stated lore.
Since we're rocking with the act of necromancy now, it would be amiss to not mention the non-attunement Wraps of Unarmed Prowess (in +1, +2, and +3 variants) from the Book of Many Things, which makes unarmed strikes magical and adds their respective bonus to attacks and damage.
As far as AL is concerned, given how rule changes are typically handled there, generic "mixed ancestry characters" rules will almost assuredly replace things like half-elves and half-orcs.
Use your torches to burn them?
If absolutely nothing else (or nothing better), that group of four should have at least those in their packs.
While 1 (+ Strength mod) isn't exactly exciting amounts of damage, it's infinitely better than no damage.
Spells, including those which require attack rolls as part of their resolution process, use the Cast a Spell action, not the Attack action, so by your logic no cantrip can be used as part of the Bladesinger feature.