1) why was not it celebrated for a few years after the original feast? 2)how did the celebration of change in the 1700s? what specific years? why?

Thanksgiving, the national holiday in the United States which is celebrated on the fourth Thursday of November,  was originally celebrated in October 1621 by the Pilgrims, along with the native Americans,   after their first harvest in the New World.   Pilgrims held a Thanksgiving celebration again in 1623 because, after the original feast to which attended 90 Native Americans and 53 Pilgrims, the latter began to gather in the small harvest they had.

In the 1700s, specifically from 1774 to 1789 The Continental-Confederation Congress appointed one or more thanksgiving days each year, or in other words several national days of prayer and thanksgiving. This practice was continued until October 3, 1789, when President George Washington proclaimed and created the first Thanksgiving Day designated by the national government of the United States of America:

Finally, On October 6, 1941, the congress passed a resolution fixing the fourth Thursday of November as the date for the holiday, beginning the next year in 1942

in february 1787, congress decided that a convention should be convened to revise the articles of confederation, the nation’s first constitution. in may, 55 delegates came to philadelphia, and the constitutional convention began. debates erupted over representation in congress, over slavery, and over the new executive branch. the debates continued through four hot and muggy months. but eventually the delegates reached compromises, and on september 17, they produced the u.s. constitution, replacing the articles with the governing document that has functioned effectively for more than 200 years.