I will answer #2 first. Yes, engulfing your opponents mobile goals is legal provided you do not violate Rule <SG6> which states:
As for #1, no there is NO rule against it. But, in my opinion, it is extremely disrespectful and very poor sportsmanship to intentionally lose matches. If it could be proven that they did, in fact, intentionally lose for the purpose of being picked by the #1 Alliance in order to win the championship as the OP seems to believe, as an event partner, I would have serious talks with the coach/mentor of the team and could go so far as DQing them from the entire event. An action like this, if true, is extremely disrespectful of each of the alliance partners that they had during the qualifying rounds and, again my opinion, runs totally counter to the ethos of VEX Robotics as I have understood it for the past 11 years. Or for that matter the ethos of any sporting event! If I caught any of my teams intentionally losing a match, I would pull them aside, discuss it with them and then withdraw them from the alliance selection.
Granted, it would be difficult to prove.
To clarify: As part of one of the allied teams with 404z, I can tell you that although I do not know whether or not 404Z lost intentionally during qualifications, it wasn’t to be picked by the number one seed. 2496N had no previous affiliation with the team, and the decision to choose the team was down to adequate scouting during the qualification matches and was made on the spot. My own team had a match with 404z, we lost 77-78.
There is another post where I have responded to this discussion, and I will say here essentially the same thing. We lost because our driver had never driven before, and the nature of a defensive robot relies on its alliance to outscore the opponents. We did not lose on purpose and to be perfectly honest, we did not expect to be chosen for the elimination rounds. If anyone has further questions, please PM me.