Is there a maximal time to pass a type rating? Let's say you begin a type rating for a long haul carrier (e.g. A350 or B787) at day 1. After few days, your training stops due to external causes (airline paying your training bankrupt, all aircraft are grounded in your area due to Eyjafjöll ashes, or even in a larger area due to a pandemic such a covid19,...). 

Is there a time limit to resume your training? If so, what is the maximal allowed time between the first day of your type rating training and the day you pass it?

This question can be restricted to A350 and B787 under FAA and EASA regulations if needed.
Nope.  Not unless your employer refuses to continue training.  Legally all that’s required is that you have accomplished all the training required to meet the prerequisites per §61.39 and meet the practical test requirements per §61.43 plus meet the eligibility requirements for the grade of pilot certificate you are applying for per §61.103, §61.123, or §61.153.