Question 1: What are these safety-bolt-insert-things called? ( https://postimg.cc/Kk9f8yv5 )

Question 2: Are they necessary / when do you know if they're necessary?

Question 3: Would you trust this rack?: ( https://www.amazon.com/gp/product/B07W91NYTD/ref=sw_img_1?smid=A3RU7XXE5ZCHU&th=1 <--not an affiliate link)

I weigh 130 and lift ~150 so I wouldn't be maxing it out any time soon.

Thanks for any advice.