How to create a nether portal (and collect required resorces) in skyblock

No.

The infinite obsidian glitch which allowed you to convert redstone (dropped by witches) into obsidian was fixed in the 1.8 patch.

There is currently no way to acquire obsidian without pouring water on a lava source block, travelling to the end, or already being able to travel to the nether. Since there is no way to acquire more obsidian or lava legitimately, it is impossible to build a portal.

In skyblock, there are 3 "blocks". The first is a grass block, with one tree, and a chest containing an ice block and a bucket of lava. You can use this to create an infinite cobble generator.

There should be another island off in the distance. This "block" should be made of sand, and has a cactus, and another chest containing 10 obsidian blocks, and another bucket.

Using the obsidian found in the chest, you can make a portal.

You cannot. A portal would require 10 still lava, A.K.A. the 10 obsidian, and flint and steel. In regular skyblock you cannot get any of them. So, no, you cannot.

Yes you can without flint and steel. Just get a wooden plank block and set it on fire with lava right next to the base of the portal and youre good to go.