Okay after doing some research I will try to answer this to the best of my ability. For a disclaimer after a few hours of searching I couldn't find a source that explain the job system in detail.
1. Are jobs submitted to every guild as advertisement or only to a specific Guild?
As we already know that there is a job board in every guild hall that has a listing of jobs that are currently available to mages to complete for compensation. We can assume very important jobs that need attending to immediately are most likely posted through every guild with the idea that enough mages will look at it and someone will accept the job. For smaller jobs with smaller rewards they are most likely categorized by locale. A mage is not going to travel all the way across Fiore for a small reward. These jobs are most likely posted only in the guild closest to the area of request. Another good assumption is that every S-Class, SS-Class, 10 Year, and 100 Year jobs are all posted to every guild hall. The reason being that there are not that many S-Class mages so they would need to be posted throughout every guild hall so the few S-Class mages have a chance to see them.
2. Is every job accepted by guild? And who is responsible for this?
We can assume that not every job is accepted and completed. This is why there are 10 year and a 100 year jobs. As for how jobs are accepted it is a safe bet that the guild will contact either the Mage Council or the patron about the acceptance of the job. For an example if Natsu accepts a job he tells Mirajane and she contacts either of the two about the job being accepted. Once the job has been accepted if there are any other guilds that have the job posted they most likely are contacted to remove the job and keep it removed unless the job does not get competed.
3.Who is responsible for assigning the ranks of the jobs and giving permission to guild members to take the job if requested?
As is known there are multiple tier levels for a mage. They are as follows: Guild Master, S-Class Mage, Mage. As we have seen in the anime there was a special area in the Fairy Tail guild hall that was only accessible for the S-Class mages. This is most likely a first check system in place so that regular mages are not allowed to accept S-Class jobs. It is also very likely that the Magic Council has detailed lists on every Mage in a legal guild and knows exactly how many S-Class mages there are in every guild. Once an S-Class or above job is accepted they probably have to approve it before sending the acceptance to the patron. Communication could possibly be handled by use of Lacrima.
As stated in the wiki the Magic Council: " are responsible for the events caused by Mages." This means that all of the events or jobs that can have mage involvement are constructed by the Magic Council. It would make sense for them to rank the jobs because most of the Council are very powerful mages and should be able to gauge how easily a job can be completed.
4. How does the payment work after the jobs are completed?
Like with most job it doesn't make sense not to assume that after the job has been completed and verified the patron will send the payment to the guild. The guild will them distribute the payment to the mage.
5. What happens when the mission fails?
We see this happen with Gildarts Clive, he undergoes a 100 year job and is unable to complete the job. Like I mentioned earlier if the job is not completed it will go back on the board until the next mage accepts it.
Once again this is not a 100% for sure correct answer to this particular question. I merely put an answer together from research based on the different wiki's and situations from the anime. If I find an actual explanation as to how this works I will modify my answer accordingly.
