There is lymphatic. drainage fro the hand but the actual nodes are first encountered in the elbow, Epitrochlear nodes are at the elbow. The hand can have lymphedema but the nodes are not there.
Monitoring Centers. Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.
Not usually. Lymph nodes are superficial and deep. In the upper extremity superficial nodes are at elbow and shoulder. Deep nodes are present in the axilla or under arm. No lymph nodes are present in the hands.