I would like to know if it is possible to start and send the application process,,,,I hear it takes around 45 months for processing in Canada,,,,so can I leave Canada after being here for 2 years have the application on process
No. A PR has to stay in Canada during the whole processing time. Short vacations abroad are fine, but not years.
I was planning to stay 2 years in Canada,,,,then leave for 6 and come back the last 2 years (then its 2- 5 year periods where I am 2 years here) and by then the sponsorship would almost be finished.
This will not work. Be really careful with your residency requirements. It is not '2 years out of every 5' as you describe; you could not stay for 2 years, leave for 6, and then get back in - you will lose your PR trying to do that.
The 5-year period is always continuing. So for the first 5 years, you could stay for the first 2 years, then live elsewhere for 3, then come back in. But when you come back in, they start counting from when you left: so they consider that you have lived for 3 years outside of Canada, and so for you to live 2 years out of 5 in Canada, you must stay in Canada for the next two years - with no chance to leave, for any reason.
This is an example:
2001 in Canada
2002 in Canada
2003 in India
2004 in India
2005 In india
2006 in India
2007 in India
2008 in India
2009 in Canada
2010 in Canada
You think that because out of the 10 years, 4 have been in Canada, you have fulfilled the requirements. But that is not true, and in fact the Canadian border officials would not have let you back in to Canada in 2009, because you would have lost your PR.
For the five-year period 2001 - 2005, the requirements were met. For the five-year period 2006 - 2010, the requirements were met. But for the five-year period 2002 - 2006, only one year was spent in Canada, so the requirment was not met. Same for the five-year periods 2003 - 2007, 2004 - 2008, and 2005 - 2009.