Can this be used for an infant 3 months plus that week ghs about 20 lbs?
No, it should definitely not be used with such a small baby. This is a very simple stroller with quite a rattly frame and not a fully reclining seat (no lie-flat) - meaning a stroller for undemanding, occasional use with a toddler that sits by him- or herself without any help. Which means you should only use it from about 6-10 months AFTER your baby, without your help, sits just so. Until then, to not damage your child's neck or spine, you should be using a newborn-friendly pram that offers a completely horizontal position.
Your -very berry- Eli.