These are two steps that can facilitate sharing nodes between applications. The other options are not valid. You do not need to create node type converters for this scenario, because both applications use the same node type for accounts.

When you archive data chain objects, you need to follow a specific order based on their dependencies. The order that you archive data chain objects is: node type, hierarchy set, node set, viewpoint. You need to archive node types first, because they are independent of other data chain objects. Then you need to archive hierarchy sets that use those node types. Then you need to archive node sets that use those hierarchy sets or node types. Then you need to archive viewpoints that use those node sets or hierarchy sets. You cannot archive data chain objects in any other order or in any order, because this would cause errors or inconsistencies in your data chain. You cannot archive applications or dimensions directly, because they are not data chain objects. Reference: Archiving and Unarchiving Data Chain Objects - Oracle Help Center

Mapping keys are used to specify the source node types mapped to target node types and to define a location name to export the mapping data. The following statements are true about mapping keys: mapping keys consist of a location, source node type, and target node type; mapping keys control which dimensions are output in the source and target columns of the mapping export. The following statements are false about mapping keys: the system automatically generates mapping keys for each unique location; one mapping key is required per location. You need to manually define mapping keys for each source-to-target relationship using a unique location name.You can have multiple mapping keys for the same location if you have different source node types mapped to the same target node type. Reference: Defining Mapping Keys - Oracle Help Center1; Exporting Mapping Data - Oracle Help Center2

Lookup sets are used to associate source values, or keys, with target values that can be used in expressions for deriving properties or transforming properties in node type converters. You can configure keys and values in a lookup set for one or more applications. Lookup sets are not created during application registration, but rather as separate objects that can be shared across applications.Lookup sets are not used to group and filter nodes, but rather to map values between different applications or perspectives. Reference: Working with Lookup Sets - Oracle Help Center2

Unbound dimensions are created outside of the application registration process and do not get imported or exported. You can use unbound dimensions to manage complex data sets such as related value sets, account combinations, and multi-dimensional mappings in Oracle Enterprise Data Management Cloud. You can extract data from unbound dimensions using extracts and load data into unbound dimension viewpoints by using request load files. You cannot use unbound dimensions for importing and exporting data, because they are not bound to any external applications. Reference: Working with Unbound Dimensions - Oracle Help Center