What is the Difference Between Google Panda and Penguin Update? 
Panda Update – This update is designed to reduce rankings for low-quality sites—sites which are SEO-expertlow-value add for users, copy content from other websites or sites that are just not very useful.

Penguin Update – This Update was designed to remove/down the websites from index which were doing much more that white hat optimization like creating too many low quality backlinks, use of aggressive exact match anchor text, overuse of exact match domains, blog spam and low quality article marketing, keyword stuffing etc…

What are top SEO ranking factors? 

Quality of content on the webpage, quality and quantity of backlinks to the webpage, anchor text used in the backlinks, domain authority, social sharing metrics and some other traffic metrics like page CTR, bounce rate and average time on the webpage

What methods would you apply for decreasing the loading time of a website?

I would use external style sheets, less images (unless necessary), optimize the images and decrease the file sizes of the image without reducing the quality of the image, use CSS sprites to reduce HTTP requests etc.

How will you solve canonicalization issue or what is .htacess file?

.htacess file is used to solve the canonicalization issue of a website. It may happen that the home page of the site may take several urls like http://www.example.com/ or http://www.example.com/index.html or http://example.com/ . The search engines might treat these url as different and may divide the link juice gained by having various backlinks made with any of these 3 urls. The link juice gets divided between these three urls equally. .htacess file is created to have a single url of the home page so that the link juice is passed onto single url.