Upvote:0
The short answer is, a, sure, you must check out your luggage when you arrive, and b, you'll have to check it in again 4 days later.
(it's 99.99% unlikely the next airline will allow you to check it in four days early.)
regarding the weight, check carefully with your ongoing airline.
Upvote:2
For a layover under 24 hours, it should be possible to check your luggage through to the US and you could therefore go through the passport check and take a quick trip to the city without collecting your luggage.
However, a 4-day stopover is usually too long for that, even if the whole trip is on one ticket, so you will almost certainly have to collect your luggage in this case. I am not sure if it makes a difference regarding the allowance, you need to check that with the airline.
If your flights are not part of the same booking, the question is moot, you will have to recheck your luggage and abide by the rules of the second airline in any case.