Can  H4 visa holders study in the US?
Yes, H4 visa holders can study in the US in any field. However, they are not allowed CPT (Curricular Practical Training), OPT(Optional Practical Training), On/Off campus jobs, or Scholarships. In order to utilize these benefits the visa  needs to be converted to  F1 visa (International student visa).

Can  H4 visa holders search for a H1B visa sponsor/ employer   in the US?
Yes, H4 visa holders can search for a H1B visa sponsor/ employer in the US. Now days, it has become difficult to achieve a genuine work visa sponsor both for tech and  non - tech professional H4 visa holders.

Somehow if a person gets a H1B visa sponsor, the lottery makes it a chance of sheer luck. Beware of fraudulent independent job consultancies. As shared by various members of my group - you will be asked to pay for your own H1B visa ( illegal), make you  to sign a bond ( illegal), forge your resume ( illegal). In case you will receive your H1B visa via lottery, they will never share related documents with you. It could lead to a serious immigration fraud.

Will pursuing  a MS ( Masters degree)/ short  term course/certification  in the US gets H4 visa holders an  H1B visa  sponsor? 
Pursuing MS/ short term courses is a good idea to enhance your skill set and knowledge. None of them promises a H1B visa. As told by members, they didn't get a genuine H1B sponsor even after getting a MS degree from regarded schools in the US. And, now their spouses are paying back  hefty education loans. Due to the  retrogression of the visa dates, it is taking 10 -15 years to get a work permit or a Green Card. The pursued degree/ course/ certification becomes obsolete. You have to to redo the credits/ subjects which comes with a  cost.

In case you are planning to pursue Masters degree in the US, please try to get enrolled into decent and recognized state/ private schools, if  not  ivy league schools/ universities. So many education related frauds  have been witnessed where the students have been deported. Also, the day one CPT is a fraud concept.  Don't become victims of 'degree mills'. All the best!

 PS  Every school/ university/ community college  has international student  department. They are very helpful to explain any kind of visa situation without any cost. It is good to contact them for the genuine information because every  US state has different  set of rules.

Can H4 holders volunteer? 
Yes, H4 Visa holders can only volunteer with non - profit organizations without availing any monetary benefits. These must be positions are unpaid if offered to the US citizens and  permanent residents as well. There have been some instances where some organizations promised filing an H1B visa petition  for the H4 dependent and made them work voluntarily for many years but never fulfilled the promise. So beware. 

Can H4 visa holders open a bank account, and have debit/ credit cards?
You can open a basic bank account with a debit card but you can’t avail all the facilities (check with your respective bank). Credit card can be issued as an add on card on primary applicant's credit account.

Can H4 visa holders apply for a Driving license?
Most states allow for a driving license. Please check with your state’s respective DMV. 

Can H4 visa holders  start  a company/ business in their home countries?
No they cannot.  As added by many people on some online forums that H4 visa holders can start their own company without taking the salary/ profit. I don''t have any official link to support this but it is very tricky situation. Green Card is taking 10- 15 years to come so why any H4 visa holder will start  a company in the United States where he/ she will  not get anything in return. For more information contact an corporate /immigration attorney. 

 Can H4 visa holders work from home?
H4 visa holders  are not allowed to work from home because they  are not authorized  to generate any kind of income from any source. They are not allowed to work anywhere.