The short answer: Yes, Regains can absolutely help you bulk up at any age. BUT please remember the key to bulking is doing heavy resistance training and making sure you're consuming more calories than you're burning (aka Total Daily Energy Expenditure or TDEE). Regains is a force multiplier in this process because it increases the natural production of human growth hormone which will help your workouts & recovery, strengthens your bones/joints/tendons/ligaments (lessens injuries), and promotes lean body mass.The long answer: If you do not consume more calories that you burn, it is physically impossible to bulk/put on weight. As for what you need to consume, this is different for everybody. No matter what any of these diet zealots (keto, paleo, carnivore, vegan, etc.) say there is no one size fits all in terms of diet. There are libraries full of books on nutrition that can't be covered in a single answer here. The important part is you find a way of eating that fits best with your lifestyle AND allows you to consume an excess of calories.For your heavy resistance training:I'm not sure how far along you are in your journey, but if you consider yourself a beginner or even a novice, I would highly recommend Mark Rippetoe's Starting Strength powerlifting routine. It will bring you the size and strength that lays the foundation for any/all future programs.Of course not everyone is able to make it to the gym right now due to lockdowns and quarantines. If this is the case and you don't have a home gym setup, there's always bodyweight exercises. We highly recommend the reddit's bodyweightfitness, Recommended Routine as a start.In summary:(EAT More than you need + Lift heavy things) * REGAINS = BULK & GET SWOLE