Nothing it's a reward, you can wield it, then go onto your equipped items screen then right-click and click operate to have your character emote with it.
There are many websites where one can get advice on completing a Runescape quest. The Runescape website itself offers advice as does the website Tip.It.
Zanaris after completing the "Lost City" quest
You will receive 3 Quest Points + 700Gp for completing this quest.
Completing this quest, you will receive:5 Quest Points200 Crafting ExperienceA Gold Bar
After Completing the Quest Fremminik trials begin the quest Fremminik isles then go to neitiznot and the yaks are there
If by "backpack" you mean "Ava's Attractor", this can be obtained by completing the Animal Magnetism quest.
For completing Ernest the Chicken, you get 4 Quest Points, 3000 gold pieces, 10 eggs and 300 feathers.
You receive the trowel after completing the level 1 test. For further help on this quest check the related links.
You can make a Blurite Sword in RuneScape as long as you are completing the quest The Knight's Sword. After you complete the quest you cannot obtain the sword again as you cannot trade the item with other players.
By completing the Giant Dwarf quest you will have access to the trapdoor, which leads to Keldadrgim.
This might be just for members but... talk to him after a while of completing the quest and he will give you something.
Completing the "Tree Gnome Village" quest will allow you to talk to and use the Spirit Tree's that are placed around Runescape, whilst doing the "Grand Tree" quest will allow you to use the gliders.