I'm basically trying to keep 5 columns of my list locked(uneditable) while the last column editable. I'm a beginner and thought this would be the easiest way to achieve this. Do kindly suggest any other alternative if possible.
This is not possible out of the box. You can limit it but not block it. ie User may still find a away of editing it if its smart.
Sharepoint is not transactional system and doesn't have something called field level security.
Now what you can do.
I have delivered something similar in the past using InfoPath forms. WIht IP you can specify which IP view is showed for new and edit form. On 'New' view you make all the fields editable. On the Edit view you make only the last column editable.
But with any of those options user can still go to the list switch to the datasheet view and edit value - so you can limit it but not block it as mentioned earlier.
To make the field read only on the edit form, you can use the script editor on Edit item page.
Add below code in the script editor:
You can repeat the read only statement for all other fields you want to make ready only(just make sure you are using right jquery selector).
Use following link to add script editor on page: