Is your current post already filled? I'm in the EU and filling positions left by people resigning has taken months. Talk to your old manager and HR. They might be more desperate than they appear.
Stayed with that company for another 4 years (7.5 in total). It'll vary based on a lot of factors. Very few employers would begrudge someone going for a huge pay rise FAANG opportunity, and the fact that they got the role means they're good material.
As always it's going to depend on a huge number of factors. It doesn't have to be negative though.
Highly depends on their behaviour and value to the company and colleagues. If they're valuable and well liked it could be an option.
Our industry is not small but we all know people in rival companies (semi-conductor, EU) and a lot of management have left to work for competitors at one point and returned. Unless you work for a seriously petty manager or an unprofessional family size company that holds grudges, leaving and returning should not be a big deal.
I only know one major US tech company with an explicit “do not rehire” policy (unless you are someone exceptional) and you probably don’t want to work there, no matter how shiny the brand is.
If you left on good terms, because you wanted to develop your career and your employer understood that. Jobs for life aren't a thing anymore, no one can seriously expect their employees to faithfully remain loyal until they get made redundant.
Hell it could even be good as it shows that the op is serious about moving up.
Now you could be right, but the op still has options to get out in that eventuality anyway.