Yes, you can use a branch multiple times as long as there is at least one leaf and a growing shoot (possibly strain dependent). Just had some success in a bubbler with a few cut that way. As for multiple tops I believe that is age/strain related, once they mature the leafs and branches become...
The only problem I've ever seen with old nutes is that some will come out of solution depending on the ph and mabey temps to a degree. Bloom ferts are of a lower ph so will stay mixed for longer. Had an issue with some FF veg nutes coming with a 1/8in crust on the bottom, just poured it into a...
Cancer is tough, I've had a few family members who have battled it and one that has gotten the upper hand. Another thing cancer is, is big business. If you have any doubt about that look into The Gerson Therapy (Max Gerson), good info that has been effectively discredited/buried for 50+ years...