In regards to your questions.
1. It's safe to have a product or two come to your address every now and again, but frequenting the same company with the same address will start to generate red flags(something you certaintly want to avoid).
2. Read above. It's never 100% safe but I'd say every 6 months from each company you intend on using.
3. I wouldn't order more than 1 product at a time as it's already a risky activity to take part in the first place.
4. You really don't want to have bulk amounts of Logitech or any other companies products shipped to your house. It's extremely suspicious and can get you in trouble. Remember nothing is 100% okay.
Be safe regardless of your decision to partake in such activities. I wish you the best.