kono zisyoapuri ha mae no yori wakariyasui desu.

より marks the thing being compared against. In English, it usually corresponds to than.

So:

• 前のより = than the previous one

In this sentence, the structure is:

• A は B より adjective です
• A is more adjective than B

So:

• この辞書アプリは前のより分かりやすいです。
• This dictionary app is easier to understand than the previous one.

前の means the previous ... or the earlier ....
Japanese often leaves out a noun when it is obvious from context.

So 前のより is a shortened version of something like:

• 前のアプリより = than the previous app
• 前の辞書アプリより = than the previous dictionary app
• 前のバージョンより = than the previous version

Because the listener already knows what is being compared, Japanese can simply say 前の by itself.

In natural English, this is like saying:

• the previous one
• the earlier one

Here, の connects 前 to an implied noun.

• 前 by itself = before / front / previous
• 前の + noun = previous noun

Examples:

• 前の本 = the previous book
• 前の人 = the person before me
• 前のアプリ = the previous app

In your sentence, the noun after 前の is omitted because it is understood. So 前の effectively means the previous one.

分かりやすい is made from:

• 分かる = to understand
• やすい = easy to do

So literally, it means something like:

• easy to understand

It is often used for things like:

• explanations
• books
• apps
• websites
• instructions

So for an app, 分かりやすい suggests that it is clear, intuitive, or easy for the user to understand.

Because 分かりやすい is much more specific.

• やさしい / 易しい = easy
• 分かりやすい = easy to understand

If you are talking about an app, dictionary, explanation, or interface, 分かりやすい is usually the better word because it focuses on clarity and understandability.

So this sentence is not just saying the app is easy in some vague sense. It says it is easier to understand / easier to use intuitively.

は marks the topic of the sentence.

• この辞書アプリは = as for this dictionary app...

The sentence is then making a comment about that topic:

• 前のより分かりやすいです
• it is easier to understand than the previous one

So は is not directly the same as English is. It sets up what the sentence is about.

Because 分かりやすい is an い-adjective.

With い-adjectives, you can add です for politeness, but the adjective itself does not change in this form:

• 分かりやすい = easy to understand
• 分かりやすいです = easy to understand (polite)

You do not say:

• 分かりやすいだです ❌
• 分かりやすいだ ❌

So this is a normal pattern:

• 高いです
• 面白いです
• 分かりやすいです

In Japanese comparisons, you usually do not need a separate word for more.

The pattern:

• A は B より adjective already means
• A is more adjective than B

So:

• このアプリは前のより分かりやすい naturally means
• This app is easier to understand than the previous one

The comparison is built into the より structure.

Yes, a little.

English:

• This dictionary app is easier to understand than the previous one.

Japanese:

• This dictionary app
  • than the previous one
    • easy to understand

So the comparison phrase with より comes before the adjective:

• この辞書アプリは
• 前のより
• 分かりやすいです

That word order is completely normal in Japanese.

Yes, but it is somewhat shortened.

この辞書アプリは前のより分かりやすいです。 is understandable and natural in casual real usage when the omitted noun is obvious.

However, learners will also often see fuller versions like:

• この辞書アプリは前のアプリより分かりやすいです。
• この辞書アプリは前のものより分かりやすいです。
• この辞書アプリは前のバージョンより分かりやすいです。

These make the comparison target more explicit.

So the original sentence is fine, but it relies on context.