About 4-5 days if kept in the fridge (come on people use your nose and your common sense!)
If it still smells good then it is OK. Heat it up properly before eating.
Ricotta cheese is a good substitute for cottage cheese in lasagna.
it is good
A red wine would ordinarily be enjoyed with lasagna.
meats can not be saved for longer than 3-5 days if it is not cooked. If it is already cooked than not longer than a week.
If you are looking for a good lasagna recipe you should try foodnetwork website. They have lots of great Italian recipes including lasagna. You could also try allrecipes website as well.
triangle lasagna and no
Salad, french bread
Cottage cheese or a mixture of cream cheese and Greek yogurt can be good substitutes for ricotta cheese in lasagna.
There are many good recipe websites at which one can find good recipes. A very popular one is allrecipes.com but there are many others to choose from to find good lasagna recipes.
2-3 days
yes it is. especially if it has already been cooked. fish can only stay good for so long.