It was indeed a legal protest
yes
Yes, the 1st amendment gives the freedom of speech which includes protest.
Picket, boycott, speech.
They have the 1st amendment right to protest on public property, so your answer is yes. Even though they do have the right it seems as if they are not respecting the family of the fallen solider in their protest at the funeral.
Yes and no. The 1st amendment gives citizens the right to freely and peaceably assemble. This means you are free to protest anything you would like. You can do so on public property, like the sidewalk, unless it creates some risk of safety.
Yes, it is illegal to block a highway in protest as it can disrupt traffic flow and pose a safety hazard. Individuals engaging in such actions may face legal consequences.
In the US, any public protest is legal, as long as you apply for the appropriate permits for lawful public assembly.
You, yourself can not. Join legalization groups, try to protest about it being illegal. It probably will not happen any time in this lifetime. Go to Amsterdam, it's legal.
No, it is not legal to drive through protestors. Doing so can result in criminal charges and serious consequences. It is important to respect the rights of individuals to peacefully protest.
In the USA, I believe it would be protected under Freedom of speech, if done in a protest, etc.
violent protest are protest which were very violent